1. Field of the Invention
This invention relates to an apparatus for generating large bubbles for mixing liquids stored in tanks. More specifically, this invention relates to a pivoting counterweighted bubble accumulator utilizing streaming sources of gas to create large mixing bubbles. Further, this invention relates to a configuration permitting retrofitting tanks with bubble accumulators without a need to decommission and drain the tank.
2. Description of the Related Art
It is known that it is desirable periodically to mix drinking water stored in large tanks, such as municipal water supplies, in order to reduce the likelihood of localized stagnation in such tanks. Large mixing bubbles, from 6 inches to three feet or greater in diameter, propagated through such tanks, such as described in U.S. Pat. No. 8,192,069, can advantageously provide the required mixing to prevent stagnation.
Further, in wastewater treatment, it is known that it is desirable to mix or agitate the liquid in both aerobic and anoxic stages of treatment to promote the conversion processes leading to water purification. Here also, large mixing bubbles of 6 inches to three feet or greater in diameter can advantageously provide the requisite mixing, as described in U.S. Pat. No. 7,282,141.
Large bubbles for mixing liquids in tanks have heretofore been provided by means of an accumulator, such as the large bubble-forming plates described in U.S. Pat. No. 4,595,296 to Parks, receiving relatively large volumes of air or compressed gas, typically supplied by an air compressor, the gas accumulating under and then erupting around the plate accumulator to form the large mixing bubbles. It is a limitation of the prior art that such methods require an air compressor, typically with a fairly large motor of three horsepower or greater, to supply the volume and pressure of gas necessitated by the accumulator design in order to create sufficiently large mixing bubbles.
It is desirable to create sufficiently large mixing bubbles using an air source that is more energy efficient than the air compressor required by the prior art. Simple blowers, such as those already in use to create small aeration bubbles in the aerobic treatment of wastewater utilize motors on the order of one horsepower, are significantly more energy efficient than the air compressors used in the prior art generation of large mixing bubbles. If an accumulator can use the air from blowers in aerobic treatment facilities, no additional source of air is needed for the accumulator in such applications. In any case, it is desirable to have an accumulator apparatus that can utilize such blowers, rather than air compressors, as the source of air for generating large mixing bubbles.
Prior art bubble mixers, such as U.S. Pat. Nos. 4,595,296 and 6,629,773 to Parks, require installation of accumulators in the bottom of the target tanks, a process entailing the decommissioning and draining of the tank when the tank is retrofitted with the bubble mixers. It is desirable to have a bubble mixer configuration that enables the retrofitting of existing tanks without requiring the tank to be drained.
Described herein below are accumulators that can utilize air supplied by blowers to generate large mixing bubbles. Also described below is a bubble mixer configuration that can be used with either prior art accumulators or the newly invented accumulators described herein to retrofit an existing tank without requiring the draining of the tank.